It’s certainly possible. US officials publicly will only say that they are investigating the matter and that no legal options have been ruled out. But an indictment in such an important federal matter would be handed down by a grand jury, and grand jury proceedings are secret, notes Stephen Vladeck, an expert in national security law at American University. There may be an empaneled grand jury considering the Assange case right now.

“We wouldn’t know what they’re doing until the whole thing is concluded,” he says.

A judge could order an indictment of Assange sealed until such time as the US is able to apprehend him, or until he is in custody in a nation from which he is likely to be extradited. The purpose of such secrecy would be to keep the WikiLeaks chief from going even further underground.

At least one prominent US legal analyst thinks this is just the sort of thing that is going on.

“I would not be at all surprised if there was a sealed arrest warrant currently in existence against [Assange],” said CNN legal expert Jeffrey Toobin on Wednesday. “That question is whether the American authorities can find him and bring him back to the United States for trial.”

In recent days US military officials have been talking about the WikiLeaks matter as if more is going on, legally speaking, than may meet the eye. Secretary of Defense Robert Gates has said that the military has enlisted FBI agents in its investigation of the matter, which could mean that someone who is not a uniformed US military person is about to be charged, or has been.

Army Pfc. Bradley Manning, an alleged source of WikiLeaks material, was arrested in Iraq last May and has been charged with providing classified information to an unauthorized source.

On Thursday, Swedish prosecutors won a round in their legal battle against the WikiLeaks founder, as Sweden’s Supreme Court upheld the order to detain him.

Assange is accused in Sweden of rape, sexual molestation, and coercion in a case dating from August. Assange’s lawyers have vehemently denied the allegations, saying they stem from consensual encounters. (Editor's note: An earlier version of this story referred to charges against Assange. He has not been charged.)

According to British media reports, Assange has been in Britain since October, and has provided police with his contact details. A WikiLeaks spokesman on Thursday said only that Assange is working on a new project at a secret location.